Bridge supporting structure having reinforced concrete elements formed along a catenary line

ABSTRACT

A MULTI-SECTION BRIDGE SUPPORTING STRUCTURE HAVING REINFORCED STEEL CONCRETE ELEMENTS EXTENDING ALONG A CATENARY LINE AND WHICH ARE DISPOSED BETWEEN A PAIR OF ABUTMENTS OR INTERMEDIATE COLUMNS AND WHOSE REINFORCING MATERIALS ARE ANCHORED THEREIN, WHERE THE STEEL CONCRETE SUPPORTING ELEMENTS CONSTITUTE THE SUPPORTING CONSTRUCTION FOR A TORSION RESISTING BOX GIRDER ANCHORED IN THE ABUTMENTS WHICH IS OF SUBSTANTIALLY CONSTANT STRUCTURAL HEIGHT AND WHICH CARRIES THE RUNWAY.

Feb. 9, 1971 HNSTERWALDER ETA'L 3,561,178

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United States Patent Office US. Cl. 52223 8 Claims ABSTRACT OF THE DISCLOSURE A multi-section bridge supporting structure having reinforced steel concrete elements extending along a catenk ary line and which are disposed between a pair of abutments or intermediate columns and whose reinforcing materials are anchored therein, where the steel concrete supporting elements constitute the supporting construction for a torsion resisting box girder anchored in the abutments which is of substantially constant structural height and which carries the runway.

BACKGROUND OF THE INVENTION The invention relates to bridge supporting structures of reinforced concrete. More in particular, the invention relates to a single or multi-section bridge supporting structure having steel concrete supporting elements formed along a catenary line that are each anchored between two abutment supports and/or intermediate columns wherein the armoring or reinforcing members are anchored.

A suspension bridge is known from German Pat. 1,046,650 Whose runway extends over and approximately parallel to the supporting elements that span the space between at least two abutments and are formed along a catenary line where the carrying members are arranged in a prestressed concrete slab that forms the roadway or its base structure and which constitute the tensioning elements of this slab. Here the tensioning or stressing elements of the concrete slab are anchored in the abutments.

The proposal was made for the first time in this patent specification to use a freely suspended band of reinforced concrete directly as a runway or as the basic structure for the same. Although the fundamental principle of this proposal must be considered as being advantageous and progressive for static and economic reasons, there result in the practical application certain difficulties which above all reside in the fact that the gradient of the runway cannot be freely chosen. This limits the possibilities of application of this form of construction. Beyond that, one sided trafiic loads result in very high border or edge stresses which result in excess dimensioning of the entire supporting structure. This adversely affects the great economic possibilities of this form of construction.

SUMMARY OF THE INVENTION It is an object of the invention to provide a possibility of enlarging the field of application of this form of con struction that is statically and economically very advantageous and above all to make possible the use of a straight line roadway gradient.

In accordance with the invention it is proposed for the further development and improvement of the known suspension bridge to constitute the carrying elements of reinforced concrete as the supporting structure for a 3,561,178 Patented Feb. 9, 1971 torsion resisting box girder of constant structural height that is anchored in the abutments and which carries the roadway.

In accordance with the invention an entirely novel carrying structure is provided, namely, the combination of a steel concrete slab anchored in the abutments and freely suspended along a catenary line of a so-called stressed band, with a torsion resisting box girder. The box girder is anchored in the abutments and the columns, but it does not absorb the horizontal thrust of the stressed band. Its own weight is completely carried by the stressed band so that in this condition it remains free from stress. The tralfic loads are absorbed by the box girder and by the stressed band in relation to their bending resistances. The onesidedness of traffic loads has no effect on the tension or stress band because the torsional moments of the bridge resulting therefrom are transferred directly by the box girder to the abutments or columns.

In realizing the structural principle in accordance with the invention, to combine a torsion resistant box girder with prestressed concrete elements formed along a catenary line, there are essentially two possibilities of combining these two structural elements. The prestressed concrete elements may be arranged within the box girder which is supported thereon by its cover plate. The prestressed concrete elements may, however, also be brought over one or more pylons in the manner of the tension cable of a suspension bridge and the box girder may be suspended thereon by means of suspension members.

The remaining partial load of the box girder makes it possible to construct it very lightly. It can be in the form of a steel or also of a steel concrete or prestressed concrete structure. For the steel concrete construction, Where it is also possible to use light concrete, it constitutes a very great part of the armoring or reinforcing means. The advantageous distribution of splits obtained thereby produces such a great expansibility of the box girder that it can be designed gapless from abutment to abutment and connected with the pylons or columns. If it is prestressed longitudinally, which is also possible, one or more expansion gaps are provided.

In the embodiment where the tension band is in the form of suspended cables of a suspension bridge and the box girder anchored in the abutments is suspended from this band, it is of particular significance if the stress band is connected at its lowest point with the box girder in a manner preventing displacement in horizontal direction. This achieves an effective stiffening of the catenary line for the traffic loads and flutter vibrations of the bridge caused by the wind pressures.

BRIEF DESCRIPTION OF THE DRAWINGS Further advantages and objects of the invention will become apparent from the following descriptions of the embodiments of the invention illustrated in the accompanying drawings in which:

FIG. 1 is a section taken along a two section bridge supporting structure Where the tension band is arranged Within the box girder,

FIG. 2 is a partial longitudinal section of a bridge supporting structure similar to that in FIG. 1 where the tension band is anchored in cantilevering trusses,

FIG. 3 is a cross section taken along line III-III in FIG. 1,

FIG. 4 is a further embodiment where the tension band follows the lines of the suspension cable of a suspension bridge,

FIG. 5 is a section along line V-V in FIG. 4,

FIG. 6 is a cross section along lines VIVI through the tension band forming the supporting construction drawn to a larger scale, and

FIG. 7 is a longitudinal section along line VII-VII taken through the supporting element in accordance with FIG. 6.

DESCRIPTION OF THE INVENTION In the bridge illustrated in FIG. 1 a steel concrete slab in the form of a tension band 4 is disposed between bridge supports such as two abutments 1 and 2 and an intermediate column 3, the supporting members 5 of which are anchored in the abutments 1, 2. The supporting members 5 which suitably are made of prestressed elements such as are conventional in prestressed concrete construction are arranged as densely as possible and for the purpose of stabilizing them and protecting them against rust, they are encased in concrete.

The tension band 4 which in the embodiment in accordance with FIG. 1 is split into two parts 4' and 4" (FIG. 3) extending at a small distance from and parallel to one another, and its entire length is disposed within a closed box girder 6 that is supported by means of slender struts 7 upon the band components 4, 4". The box girder 6 is made of relatively thin lateral Walls 8 and a bottom plate 9 which is likewise thin, as well as of the deck panel 10 which is somewhat larger in cross section and which is simultaneously formed as a runway structure.

The catenary forces of the tension bands 4, 4" which hang along a catenary line are transferred into the abutments by the carrying members 5 that extend into the abutments 1, 2 so that the box girder 6 is free of horizontal compression forces from these catenary forces. The box girder 6 is anchored in the abutments 1, 2 without introducing between them expansion gaps. Apart from those areas between the individual struts 7 where minor bending moments arise, the box girder 6 is essentially tensionless in the area of load application of its own weight. In order to absorb the tensions that result from the changes in temperature, it is provided with very heavy reinforcing members.

In order that the height of the box girder does not become too great with larger span widths the possibility is provided of anchoring the span band 4 in trusses 11 which extend from the abutments 1 or the column 3 inside the box girder (FIG. 2). In this manner, if the same sag is maintained, the span width of the freely suspended band 4 is decreased and thus either the catenary force is reduced or an increase of the span width is afforded.

In accordance with the invention it is also possible, however, by means of the embodiment illustrated in FIGS. 4 and 5 to provide a tension band 12 between two abutments 13 and 14 and two pylons 15. The box girder 16 is then suspended by means of suspension struts 17 from the tension band 12 which suitably also comprises two spaced parts 12', 12". Also, here the structural principle, which departs from the construction principle of ordinary bridges is followed to anchor the supporting rods 18 of the tension band components 12' and 12" in the abutments and to assign to the box girder 16, which is anchored in the abutments 13, 14 only the absorption of the tensions resulting from the differences in temperature. The traffic loads are then absorbed in common by the box girder 16 and the tension band 12.

FIGS. 6 and 7 show sections through a tension band part 12. The tension rods 18 which in the embodiment illustrated are steel rods that are provided at least at the ends with threads, are arranged so closely to each other that there is just sufiicient space for the connecting sleeves 19. It is possible and at times also advantageous to connect the tension band 12 at its lowest point 20 in the center of the supporting structure with the box girder 16. As a result, changes in form that are caused by wind pressures and which could cause fluttering and vibrations of the band are side tracked into the box girder.

It is particularly advantageous to construct the box girder 6 or 16 upon construction of the abutments and of the steel concrete elements in sectional free cantilever construction with the help of the scaffolding that is movable along the supporting portion which has already been completed.

Having now described our invention with reference to the embodiments illustrated, what we desire to protect by letters patent is set forth in the following claims.

We claim:

1. A bridge sructnre having at least one portion defining a freely suspended steel reinforced concrete support formed along a catenary line defining a tension band between bridge supports such as abutments, columns or the like, said tension band having reinforcing members anchored in said bridge supports, and a torsion resistant box girder of generally constant structural height supported on and extending throughout the span between said bridge supports, adapted to support a roadway and where said tension band is disposed within said box girder.

2. A bridge structure in accordance with claim 1, where said box girder has a deck panel, and struts are provided supporting said deck panel on said tension band.

3. A bridge structure in accordance with claim 2, comprising trusses cantilevering out from said bridge supports and extending into the interior of said box girder.

4. A bridge structure in accordance with claim 1, where said tension band is constituted in the manner of a tension cable of a suspension bridge and extends over at least one pylon and suspension struts are provided supporting said box girder.

5. A bridge structure in accordance with claim 4, where said box girder is made of lightly reinforced concrete and extends between said bridge supports without expansion gaps.

6. A bridge structure in accordance with claim 4, where said box girder is prestressed in the longitudinal direction and is provided with expansion gaps.

7. A bridge structure in accordance with claim 1, where said tension band is connected in the area of its greatest sag in horizontal direction with said box girder.

8. A bridge structure in accordance with claim 4, where said tension band is connected in the area of its greatest sag with said box girder in horizontal direction.

References Cited UNITED STATES PATENTS 1,453,084 4/1923 Strauss 14-19 FOREIGN PATENTS 31,431 8/1907 Austria 52l74 1,020,094 2/1966 Great Britain 14-19 642,128 6/1962 Canada 52l74 689,266 5/1930 France 52l74 1,046,650 12/1958 Germany 52l74 FRANK L. ABBOTT, Primary Examiner I. L. RIDGILL, JR., Assistant Examiner U.S. c1. XR. 14 19; s2 574 

